Application of capacitive deionization technology to the removal of sodium chloride from aqueous solutions

Capacitive deionization has been developed as a promising desalination alternative for removing ions from aqueous solutions. In this study, the evaluation of capacitive performance was carried out by galvanostatic charge/discharge and cyclic voltammetry experiments. The good capacitive and electrosorption behaviors suggest carbon aerogel not only treated as an electrical double layer capacitor, but also as a potential electrode in capacitive deionization processes. Also, the capacitive deionization characteristics indicate that electrosorption/regeneration can be controlled by polarization and depolarization of each electrode. It implies that sodium and chloride ions are electrostatically held to form electrical double layer on the surface of charged electrodes. The electrosorption performance at different applied voltages and solution concentrations was investigated. It is found that the removal of sodium chloride increases with increasing applied voltage and solution concentration, resulting from stronger electrostatic interactions, higher concentration gradient, and less double layer overlapping effect. Based on Langmuir isotherm, the equilibrium electrosorption capacity at 1.2 V is determined as 270.59 μmol/g. Under this condition, due to the presence of micropores associated with the double layer overlapping, the effective surface area for electrosorption of ions at 1.2 V is estimated in the range of 12.18–14.25 % of the Brunauer–Emmett–Teller surface area. The results provide a fundamental understanding of electrosorption of ions and help promoting capacitive deionization technology for water purification and desalination.     

电渗排水固结中电极材料的对比试验

采用辽宁沿海地区淤泥质软土对铁、铜、铝和新型复合电极等不同电极材料进行室内电渗排水固结试验,从有效电势、电流、排水量与排水速率、能耗、电渗后土体含水率和承载力等对电渗效果进行分析。新型复合电极材料是由碳纤维、塑料排水板与铁片组成,其充分利用各种材料的优点,既解决了铁与碳纤维直接相连通电后易断的问题,又解决了电极腐蚀严重的问题。多组试验结果表明：新型复合电极材料的电渗排水固结使土体的加固强度提升较高,且相对均匀,加固强度达到160 kPa以上的土体面积占加固总面积的75%,说明新型复合电极材料的优越性。金属电极的腐蚀较为严重,且主要发生在阳极。根据电渗后阳极的腐蚀比,新型复合电极的腐蚀量明显低于金属电极,且新型复合电极可提高加固效果,节约电极材料成本。     

充分利用咸水、微咸水改善沧州水环境

沧州水资源严重匮乏,不得不大量超采深层地下水,并由此而带来了地面下沉、机井报废、防汛抗旱能力下降等一系列环境地质问题,在特定的地理条件下,沧州区域内咸水、微咸水较为丰富,本文针对上述现状,探讨利用抽成补淡、咸淡混浇、咸水淡化等技术措施,充分利用咸水、微咸水,节约淡水资源,实现对沧州水环境的修复。     

电容去离子化去除地下水中镉的影响因素

以高比表面积活性炭作为吸附剂制备电容电极,研究电容去离子化（CDI）对地下水中镉的吸附性能。分别探讨了镉初始质量浓度、体系供电电压、地下水中常见阳离子种类对CDI去除镉的影响。结果表明,CDI吸附镉符合准二级吸附动力学、满足Langmuir等温吸附方程,CDI对镉的吸附为单分子层吸附。吸附量随镉初始质量浓度的升高而增加;在低质量浓度时,较高的供电电压会提高初始阶段的吸附速率,但对电极的最终吸附量无显著影响;地下水中主要阳离子的存在增加了体系的电导率,从而促进了CDI对镉的吸附,提高了镉的吸附速率和去除率。     

Survey efficiency of electrocoagulation on nitrate removal from aqueous solution

Water supply for consumption is one of the crucial objectives of water supply systems. Using of excessive fertilizer is a main source of nitrate content in water. The high amounts of nitrate in water have a determinable effect on the environment which must be removed due to drinking and industrial water standards. The purpose of this study is nitrate removal from aqueous solution by Electrocoagulation process. The applied pilot was comprised of a reservoir, electrode and power supply. In this study pH, electrical potential difference, nitrate initial concentration, total dissolved solid, kind of electrode, electrode connection methods and number of electrode were studied. Moreover, obtained optimum conditions were tested on Kerman water. The results showed that the electrocoagulation process can reach nitrate to less than standard limit. pH, electrical potential difference, total dissolved solids and number of electrodes have direct effect and initial concentration of nitrate has reverse effect on nitrate removal. This study also showed that under optimum condition, nitrate removal from Kerman water distribution system was 89.7 %. According to the results, Electrocoagulation process is suggested as an effective technique in nitrate removal.     

基于二极电阻率法的并行电法勘探技术

利用点电场的分布规律和高密度电阻率法的基本思想,从二极直流电法勘探和地震勘探的思路出发,提出了利用1个电极供电,其余电极同步测量的网络电法勘探系统,通过室内数据处理实现高密度电法的二极、温纳三极A、三极B的同步快速测量。该方法极大地缩短了现场数据采集时间,提高了电法勘探的效率。目前,该方法技术已广泛应用于地基勘察、矿井回采工作面导水裂隙带高度探测及矿井出水水源探测等工程实践中。     

Evaluation of the performance of a new freeze desalination technology

The use of desalination technologies which produce concentrated brines is acutely limited by inadequate waste brine disposal mechanisms such that the brine does not contaminate fresh water resources. The treatment of highly saline brine using freeze desalination technique trade marked as HybridICE? technology was investigated at pilot scale. The capacity of the HybridICE? process to generate fresh water by freeze desalination of brine was investigated in this study. Brine samples to feed into the HybridICE process unit were prepared in tanks with volume capacities between 1.0 and 10.0 m³ by dissolving common salt into tape water. The effects of refrigerant temperature, initial brine concentration, energy consumption were evaluated in relation to product ice quality. Feed brine samples were processed in batches in a closed system where it was continuously re-circulated to generate product ice and more concentrated residual small volume of brine stream. The quality of ice produced could be turned into potable water it terms of its low total dissolved salts and conductivity. The salt removal, based on the average chloride concentration in the ice samples, was 96 %. The energy utilization efficiency amounted to an average of ZAR 10.0/m³ water assuming energy cost of ZAR 0.39/kWh. The HybridICE? technology was shown to be a better option than other desalination technologies currently in use, in terms of energy utilization and cleaner by-products.     

Review: Some low-frequency electrical methods for subsurface characterization and monitoring in hydrogeology

Low-frequency geoelectrical methods include mainly self-potential, resistivity, and induced polarization techniques, which have potential in many environmental and hydrogeological applications. They provide complementary information to each other and to in-situ measurements. The self-potential method is a passive measurement of the electrical response associated with the in-situ generation of electrical current due to the flow of pore water in porous media, a salinity gradient, and/or the concentration of redox-active species. Under some conditions, this method can be used to visualize groundwater flow, to determine permeability, and to detect preferential flow paths. Electrical resistivity is dependent on the water content, the temperature, the salinity of the pore water, and the clay content and mineralogy. Time-lapse resistivity can be used to assess the permeability and dispersivity distributions and to monitor contaminant plumes. Induced polarization characterizes the ability of rocks to reversibly store electrical energy. It can be used to image permeability and to monitor chemistry of the pore water–minerals interface. These geophysical methods, reviewed in this paper, should always be used in concert with additional in-situ measurements (e.g. in-situ pumping tests, chemical measurements of the pore water), for instance through joint inversion schemes, which is an area of fertile on-going research.     

Cadmium (II)-selective electrode based on palm shell activated carbon modified with task-specific ionic liquid: kinetics and analytical applications

In this study, palm shell activated carbon modified with task-specific ionic liquid was used as a novel electrode component for the potentiometric determination of cadmium ions in water samples. The proposed potentiometric sensor has good operating characteristics, including relatively high selectivity towards the Cd (II) ion, a Nernstian response to Cd (II) ions in a working concentration range of 1.0 × 10^?9–1.0 × 10^?2 M, with a reasonable detection limit of 1 × 10^?10 M and a slope of 30.90 ± 1.0 mV/decade. No significant changes in electrode potential were observed when the pH was varied over the range of 4–9. A direct technique based on the use of ion-selective electrode potentiometry has been developed in our laboratory for the study of reaction kinetics and kinetic methods of analysis by continuous monitoring of the rate of production or consumption of an ion. The apparent adsorption rate constant was estimated assuming pseudo-second-order kinetics. Additionally, the proposed electrode has been successfully used for the determination of the cadmium content in real samples without a significant interaction from other cationic or anionic species.     

A multi-media planning model for assessing co-located energy and desalination plants

The co-location of desalination plants with existing or proposed power plants can bring forth economic and ecological advantages in terms of reducing the costs of water intake and reducing fish impingement. However, fossil fuel-based power plants are a source of ozone precursors and the added strain of power needed for the energy intensive desalination process increases these pollutants into the atmosphere. Furthermore, withdrawal from brackish water sources puts a stress on slowly replenishing aquifers. Additionally, the resulting concentrate is highly saline and disposal into ecologically sensitive bays and estuaries may be problematic. Balancing these limitations with the need for freshwater is of great importance for sustainability of water scarce arid and semi-arid regions and also requires a holistic multimedia impact evaluation. Therefore, an integrated system of systems approach is adopted in this study and a decision support system that integrates the flow of water, concentrate and resulting pollutants through two engineered (power plant and desalination plant) as well as three natural systems (coastal bay, aquifer and the atmosphere) is developed to study the co-location of a power plant and a desalination plant near the City of Corpus Christi in South Texas. The objective of the model is to minimize the amount of groundwater extraction and minimize the amount of water extracted from the bay to emphasize water and ecosystem conservation, respectively. These objectives, in turn, are subject to various other constraints including (1) conservation of mass; (2) air quality regulations; (3) salinity regulation policies; (4) groundwater management constraints; (5) water demand requirements; and (6) energy demand constraints. The results indicate that when conservation of the aquifer is weighted more, less water is pulled from the aquifer until later time periods. The salinity of the bay increases and creates a need for a greater amount of power necessary to process the saline water which, in turn, enhances the atmospheric loading of ozone precursors. Therefore, the conservation of groundwater scenario is limited by the air quality standards. Alternatively, when the goal is to conserve the ecological integrity of the bay while meeting freshwater demands, the model is bound by the prescribed drawdown constraint that limits the amount of water that can be extracted from the aquifer. The results from the study indicate that blending saline bay water with brackish groundwater and using cleaner burning fossil fuels that have limited air quality impacts will enhance the performance of the co-located power and desalination operations. The results of the study highlight the need for an integrated multimedia evaluation in assessing the feasibility of desalination in areas with marginal air quality.     

超大采高工作面顶板电阻率监测可行性试验

顶板覆岩破坏是造成回采工作面突水的主要原因之一,利用矿井电法进行顶板电阻率监测可以对覆岩破坏情况进行动态探查,但是超大采高工作面顶板电阻率监测面临着常规方法音频信号难以穿透、顶板监测电极埋设施工困难以及回风巷顶板监测电极难以保护等问题。为了解决上述问题,利用音频电透仪和回采工作面电阻率监测系统开展了超大采高工作面顶板电阻率监测可行性试验研究。结果显示:单极-偶极装置音频信号透视穿透距离可达340 m;锚杆可以作为监测电极进行电流发射和信号采集;可以将回风巷监测电极布置于巷道底板加以保护。在某矿超大采高工作面部署了回采工作面电阻率监测系统,信号测试结果与可行性试验的结论一致。      

Fixed-bed column study for the adsorptive removal of acid fuchsin using carbon–alumina composite pellet

The carbon–alumina composite pellet was developed for the adsorption of acid fuchsin from its aqueous solution. The composite pellet was characterized using Brunauer–Emmett–Teller method, scanning Electron Microscopy and Fourier Transform Infrared Spectroscopy. The adsorption capacity of commercial alumina, commercial activated carbon and the prepared composite pellet was investigated against acid fuchsin, and the adsorption capacity was found to be increased in the order of alumina < carbon–alumina composite pellet < activated carbon. Although the adsorption capacity of carbon–alumina composite pellets was less than that of activated carbon, the use of the pelletized form of the present adsorbent was proven to be advantageous for the use in the packed-bed column. The experimental data were fitted to Langmuir, Freundlich and Temkin adsorption isotherms, and the equilibrium behavior was well explained by Langmuir isotherm. Besides, the kinetic behavior was well predicted by pseudo-second-order kinetics. The effects of inlet dye concentration (10–20 mg/L), feed flowrate (5–15 mL/min) and bed height (2.54–7.62 cm) on the breakthrough characteristics were investigated using a fixed-bed column. The maximum removal capacity in the column study was found to be 343.87 mg/L with an initial dye concentration and flowrate of 20 and 10 mL/min according to Bohart–Adams model. The breakthrough behavior was also effectively described by the Yoon–Nelson and Clark models.     

土的电阻率室内测试技术研究

土的电阻率可反映土的组成和结构特征。室内测试是研究土电阻率的主要方法之一。本文在分析影响电阻率因素的基础上,总结了国内外现有土电阻率测试的原理与方法,介绍了作者研制的一种实用土电阻率测试仪,并通过典型试验,论证了该测试仪器的可行性,可以在室内土电阻率测试试验中应用。     

Comparison between VES and 2D imaging techniques for delineating subsurface plume of hydrocarbon contaminated water southeast of Karbala City,Iraq

Shallow vertical electrical sounding (VES) technique with Schlumberger electrode array (maximum distance between current electrodes was 50 m) through 25 VES points distributed on five traverses. Two 2D imaging lines with Wenner electrode array 30 m each corresponding to two VES traverses were conducted near well water contaminated with hydrocarbon materials at Karbala Governorate, Iraq. It is found that these techniques can give good results in delineating contaminated and clear zones but the 2D imaging technique was better in delineating the boundaries of the contaminated water plume and gave clear image of the subsurface distribution of the contaminated water vertically and horizontally.     

Development of a GIS-based catastrophe theory model (modified DRASTIC model) for groundwater vulnerability assessment

This study developed a new paradigm for groundwater vulnerability assessment by modifying the standard DRASTIC index (DI) model based on catastrophe theory. The developed paradigm was called the catastrophe theory-based DI (CDI) model. The proposed model was applied to assess groundwater vulnerability to pollution index (GVPI) in Perak Province, Malaysia. The area vulnerability index was modeled by considering the DRASTIC multiple vulnerability causative factors (VCFs) obtained from different data sources. The weights and ranking of the VCFs were computed by using the inner fuzzy membership mechanism of the CDI model. The estimated vulnerability index values of the CDI model were processed in a geographic information system (GIS) environment to produce a catastrophe theory–DRASTIC groundwater vulnerability to pollution index (CDGVPI) map, which demarcated the area into five vulnerability zones. The produced CDGVPI map was validated by applying the water quality status–vulnerability zone relationship (WVR) approach and the relative operating characteristic (ROC) curve method. The performance of the developed CDI model was compared with that of the standard DI model. The validation results of the WVR approach exhibits 89.29% prediction accuracy for the CDI model compared with 75% for the DI model. Meanwhile, the ROC validation results for the CDI and DI models are 88.8% and 78%, respectively. The GIS-based CDI model demonstrated better performance than the DI model. The GVPI maps produced in this study can be used for precise decision making process in environmental planning and groundwater management.     

Hollow Porous SiO_2 Nanocubes with Enhanced Lithium Storage Properties

The high theoretical capacity and low discharge potential of silicon have attracted much attention on Si-based anodes. Herein, hollow porous SiO2 nanocubes have been prepared via a two-step hard-template process and evaluated as electrode materials for lithium-ion batteries. The hollow porous SiO2 nanocubes exhibited a reversible capacity of 919 mAh/g over 30 cycles. The excellent property could be attributed to the unique hollow nanostructure with large volume interior and numerous crevices in the shell, which could accommodate the volume change and alleviate the structural strain during Li ions insertion and extraction, as well as allow rapid access of Li ions during charge/discharge cycling. It is found that the formation of irreversible or reversible lithium silicates in the anodes determines the capacity of a deep-cycle battery, fast transportation of Li ions in hollow porous SiO2 nanocubes is preferred to form Li2O and Si, contributing to the high reversible capacity. The hollow porous SiO2 nanocubes have great potential applications for Li-ion batteries due to their remarkable electrochemical performance and low cost.     

Removal of arsenic from contaminated water utilizing tea waste

Activated carbon is the adsorbent commonly used to remove arsenic from contaminated water. However, the problem is that it is not always available everywhere and considered expensive in developing countries. An inexpensive alternative to activated carbon can therefore aid the adequate treatment of contaminated water. Tea waste, water hyacinth and banana peel are investigated extensively in this study as the inexpensive alternative. Tea waste treated with a right proportion of aqueous FeCl₃ reagent is found to have substantially higher arsenic removing capacity (which is quantified by arsenic concentrations measured employing Double Beam Atomic Absorption Spectrophotometer) than the other two. The comparison made subsequently between tea waste and activated carbon reveals the feasibility of the utilization of tea waste. The arsenic removing capacity of tea waste treated with the right proportion of aqueous FeCl₃ reagent is found to be equal to that of the activated carbon treated with the same reagent over the continuous operative time of 2 h. The tea waste treated rightly with the same reagent also removes arsenic at acceptable capacities over extended operative times such as 4–6 h. It is therefore proposed to consider tea waste as the inexpensive alternative to activated carbon in treating arsenic contaminated water.     

A coupled chemo‐thermo‐hygro‐mechanical model of concrete at high temperature and failure analysis

A hierarchical mathematical model for analyses of coupled chemo‐thermo‐hygro‐mechanical behaviour in concretes at high temperature is presented. The concretes are modelled as unsaturated deforming reactive porous media filled with two immiscible pore fluids, i.e. the gas mixture and the liquid mixture, in immiscible–miscible levels. The thermo‐induced desalination process is particularly integrated into the model. The chemical effects of both the desalination and the dehydration processes on the material damage and the degradation of the material strength are taken into account. The mathematical model consists of a set of coupled, partial differential equations governing the mass balance of the dry air, the mass balance of the water species, the mass balance of the matrix components dissolved in the liquid phases, the enthalpy (energy) balance and momentum balance of the whole medium mixture. The governing equations, the state equations for the model and the constitutive laws used in the model are given. A mixed weak form for the finite element solution procedure is formulated for the numerical simulation of chemo‐thermo‐hygro‐mechanical behaviours. Special considerations are given to spatial discretization of hyperbolic equation with non‐self‐adjoint operator nature. Numerical results demonstrate the performance and the effectiveness of the proposed model and its numerical procedure in reproducing coupled chemo‐thermo‐hygro‐mechanical behaviour in concretes subjected to fire and thermal radiation. Copyright © 2005 John Wiley & Sons, Ltd.     

Desalination,space and power: The ramifications of Israel’s changing water geography

Desalination alters a basic premise of water geography – fresh water flows from the sea inward, rather than the other way around. But, is this observation important? To address this question it is necessary to identify the potential ramifications of the changes in the water geography brought about by desalination. Israel is used as a basis for identifying these ramifications as it has recently embarked on a large-scale desalination program. The direct readily observable implications of the three main attributes of desalination, the reversal of flow direction, the continuity of water production, regardless of weather and climate vagrancies, and its cost are first spelled out. Then the potential ramifications for internal power structures, pricing and transboundary water agreements are discussed for the Israeli and Israeli–Arab scene. It is shown that the spatial flexibility introduced by desalination may undermine existing power relations within the water sector, which were based on the previous water geography. In the Israeli case these changes may be used to undermine the monopoly power of the national water company and of its organized labor, thereby advancing a neoliberal agenda. Desalination may have also significant distributional implications, as a function of the pricing effects it may have. Finally, the new water geography raises new issues in the Israeli–Arab water scene. The general insights gained from the Israeli case are then spelled out.     

Natural salinity sources in the groundwaters of Jordan—Importance of sustainable aquifer management

In recent years, voices in Jordan became lauder to exploit the fresh to brackish deep groundwater overlain by fresh groundwater bodies. In this article the implications of such a policy on the existing fresh water bodies are worked out through studying the sources of salinity in the different aquifer systems and the potentials of salinity mobilization by artificial changes in the hydrodynamic regimes. It is concluded that extracting the groundwater of deep aquifers overlain by fresh water bodies, whether the deep groundwater is fresh to brackish, brackish or salty, is equivalent to extracting groundwater from the overlying fresh groundwater bodies because of the hydraulic connections of the deep and the shallow aquifers’ groundwaters. The consequences are even more complicated and severe because exploiting the deep groundwater containing brackish or salty water will lead to refilling by fresh groundwater leaking from the overlying aquifers. The leaking water becomes salinized as soon as it enters the pore spaces of the emptied deep aquifer matrix and by mixing with the deep aquifer brackish or saline groundwater. Therefore, the move to exploit the deep groundwater is misleading and damaging the aquifers and is unjust to future generation's rights in the natural wealth of Jordan or any other country with similar aquifers’ set-up. In addition, desalination produces brines with high salinity which cannot easily be discharged in the highlands of Jordan (with only very limited access to the open sea) because they will on the long term percolate down into fresh water aquifers.